I've attempted to alter table using pt-online-schema-change in our master-master replication environment (Percona used as a cluster). It seems, that an operation completed successfully, but inspecting MySQL logs I've found the following:

140724 20:41:49 [ERROR] Slave SQL: Error 'This version of MySQL
doesn't yet support 'multiple triggers with the same action time and
event for one table'' on query. Default database: 'forumhouse'. Query:
'CREATE DEFINER=forumhouse@% TRIGGER
pt_osc_forumhouse_xf_user_profile_del AFTER DELETE ON
forumhouse.xf_user_profile FOR EACH ROW DELETE IGNORE FROM
forumhouse._xf_user_profile_new WHERE
forumhouse._xf_user_profile_new.user_id <=> OLD.user_id',
Error_code: 1235

What may this mean? And why pt-online-schema-change ignored an error? Is it safe to use this great tool in our situation?

pt-online-schema-change version is 2.2.9. Server config:

# MySQL server variables for 127.0.0.1

auto_increment_increment = 2
auto_increment_offset = 1
autocommit = ON
automatic_sp_privileges = ON
back_log = 50
basedir = /usr
big_tables = OFF
binlog_cache_size = 32768
binlog_direct_non_transactional_updates = OFF
binlog_format = ROW
binlog_stmt_cache_size = 32768
bulk_insert_buffer_size = 8388608
character_set_client = utf8
character_set_connection = utf8
character_set_database = utf8
character_set_filesystem = binary
character_set_results = utf8
character_set_server = latin1
character_set_system = utf8
character_sets_dir = /usr/share/percona-xtradb-cluster/charsets/
collation_connection = utf8_general_ci
collation_database = utf8_general_ci
collation_server = latin1_swedish_ci
completion_type = NO_CHAIN
concurrent_insert = AUTO
connect_timeout = 10
datadir = /var/lib/mysql/
date_format = %Y-%m-%d
datetime_format = %Y-%m-%d %H:%i:%s
default_storage_engine = InnoDB
default_week_format = 0
delay_key_write = ON
delayed_insert_limit = 100
delayed_insert_timeout = 300
delayed_queue_size = 1000
div_precision_increment = 4
enforce_storage_engine = 
engine_condition_pushdown = ON
error_count = 0
event_scheduler = OFF
expand_fast_index_creation = OFF
expire_logs_days = 1
external_user = 
extra_max_connections = 1
extra_port = 0
fast_index_creation = ON
flush = OFF
flush_time = 0
foreign_key_checks = ON
ft_boolean_syntax = + -><()~*:""&|
ft_max_word_len = 84
ft_min_word_len = 4
ft_query_expansion_limit = 20
ft_stopword_file = (built-in)
general_log = OFF
general_log_file = /var/lib/mysql/rhino0.log
group_concat_max_len = 1024
have_compress = YES
have_crypt = YES
have_csv = YES
have_dynamic_loading = YES
have_flashcache = YES
have_geometry = YES
have_innodb = YES
have_ndbcluster = NO
have_openssl = DISABLED
have_partitioning = YES
have_profiling = YES
have_query_cache = YES
have_response_time_distribution = YES
have_rtree_keys = YES
have_ssl = DISABLED
have_symlink = YES
hostname = rhino0.forumhouse.ru
identity = 0
ignore_builtin_innodb = OFF
init_connect = 
init_file = 
init_slave = 
innodb_adaptive_flushing = ON
innodb_adaptive_flushing_method = estimate
innodb_adaptive_hash_index = ON
innodb_adaptive_hash_index_partitions = 1
innodb_additional_mem_pool_size = 8388608
innodb_autoextend_increment = 8
innodb_autoinc_lock_mode = 2
innodb_blocking_buffer_pool_restore = OFF
innodb_buffer_pool_instances = 1
innodb_buffer_pool_populate = OFF
innodb_buffer_pool_restore_at_startup = 0
innodb_buffer_pool_shm_checksum = ON
innodb_buffer_pool_shm_key = 0
innodb_buffer_pool_size = 85899345920
innodb_change_buffering = all
innodb_checkpoint_age_target = 0
innodb_checksums = ON
innodb_commit_concurrency = 0
innodb_concurrency_tickets = 500
innodb_corrupt_table_action = assert
innodb_data_file_path = ibdata1:10M:autoextend
innodb_data_home_dir = 
innodb_dict_size_limit = 0
innodb_disallow_writes = OFF
innodb_doublewrite = ON
innodb_doublewrite_file = 
innodb_fake_changes = OFF
innodb_fast_checksum = OFF
innodb_fast_shutdown = 1
innodb_file_format = Antelope
innodb_file_format_check = ON
innodb_file_format_max = Antelope
innodb_file_per_table = OFF
innodb_flush_log_at_trx_commit = 1
innodb_flush_method = 
innodb_flush_neighbor_pages = area
innodb_force_load_corrupted = OFF
innodb_force_recovery = 0
innodb_ibuf_accel_rate = 100
innodb_ibuf_active_contract = 1
innodb_ibuf_max_size = 42949656576
innodb_import_table_from_xtrabackup = 0
innodb_io_capacity = 200
innodb_kill_idle_transaction = 0
innodb_large_prefix = OFF
innodb_lazy_drop_table = 0
innodb_lock_wait_timeout = 50
innodb_locking_fake_changes = ON
innodb_locks_unsafe_for_binlog = OFF
innodb_log_block_size = 512
innodb_log_buffer_size = 8388608
innodb_log_file_size = 52428800
innodb_log_files_in_group = 2
innodb_log_group_home_dir = ./
innodb_max_bitmap_file_size = 104857600
innodb_max_changed_pages = 1000000
innodb_max_dirty_pages_pct = 75
innodb_max_purge_lag = 0
innodb_merge_sort_block_size = 1048576
innodb_mirrored_log_groups = 1
innodb_old_blocks_pct = 37
innodb_old_blocks_time = 0
innodb_open_files = 300
innodb_page_size = 16384
innodb_print_all_deadlocks = OFF
innodb_purge_batch_size = 20
innodb_purge_threads = 1
innodb_random_read_ahead = OFF
innodb_read_ahead = linear
innodb_read_ahead_threshold = 56
innodb_read_io_threads = 4
innodb_recovery_stats = OFF
innodb_recovery_update_relay_log = OFF
innodb_replication_delay = 0
innodb_rollback_on_timeout = OFF
innodb_rollback_segments = 128
innodb_show_locks_held = 10
innodb_show_verbose_locks = 0
innodb_spin_wait_delay = 6
innodb_stats_auto_update = 1
innodb_stats_method = nulls_equal
innodb_stats_on_metadata = ON
innodb_stats_sample_pages = 8
innodb_stats_update_need_lock = 1
innodb_strict_mode = OFF
innodb_support_xa = ON
innodb_sync_spin_loops = 30
innodb_table_locks = ON
innodb_thread_concurrency = 0
innodb_thread_concurrency_timer_based = OFF
innodb_thread_sleep_delay = 10000
innodb_track_changed_pages = OFF
innodb_use_atomic_writes = OFF
innodb_use_global_flush_log_at_trx_commit = ON
innodb_use_native_aio = ON
innodb_use_sys_malloc = ON
innodb_use_sys_stats_table = OFF
innodb_version = 5.5.37-35.0-35.0
innodb_write_io_threads = 4
insert_id = 0
interactive_timeout = 28800
join_buffer_size = 131072
keep_files_on_create = OFF
key_buffer_size = 8388608
key_cache_age_threshold = 300
key_cache_block_size = 1024
key_cache_division_limit = 100
large_files_support = ON
large_page_size = 0
large_pages = OFF
last_insert_id = 0
lc_messages = en_US
lc_messages_dir = /usr/share/percona-xtradb-cluster/
lc_time_names = en_US
license = GPL
local_infile = ON
lock_wait_timeout = 31536000
locked_in_memory = OFF
log = OFF
log_bin = ON
log_bin_trust_function_creators = OFF
log_error = /var/log/mysqld.log
log_output = FILE
log_queries_not_using_indexes = OFF
log_slave_updates = OFF
log_slow_admin_statements = OFF
log_slow_filter = 
log_slow_queries = OFF
log_slow_rate_limit = 1
log_slow_rate_type = session
log_slow_slave_statements = OFF
log_slow_sp_statements = ON
log_slow_verbosity = 
log_warnings = 1
log_warnings_suppress = 
long_query_time = 10.000000
low_priority_updates = OFF
lower_case_file_system = OFF
lower_case_table_names = 0
max_allowed_packet = 1048576
max_binlog_cache_size = 18446744073709547520
max_binlog_files = 0
max_binlog_size = 1073741824
max_binlog_stmt_cache_size = 18446744073709547520
max_connect_errors = 10
max_connections = 151
max_delayed_threads = 20
max_error_count = 64
max_heap_table_size = 16777216
max_insert_delayed_threads = 20
max_join_size = 18446744073709551615
max_length_for_sort_data = 1024
max_long_data_size = 1048576
max_prepared_stmt_count = 16382
max_relay_log_size = 0
max_seeks_for_key = 18446744073709551615
max_slowlog_files = 0
max_slowlog_size = 0
max_sort_length = 1024
max_sp_recursion_depth = 0
max_tmp_tables = 32
max_user_connections = 0
max_write_lock_count = 18446744073709551615
metadata_locks_cache_size = 1024
min_examined_row_limit = 0
multi_range_count = 256
myisam_data_pointer_size = 6
myisam_max_sort_file_size = 9223372036853727232
myisam_mmap_size = 18446744073709551615
myisam_recover_options = OFF
myisam_repair_threads = 1
myisam_sort_buffer_size = 8388608
myisam_stats_method = nulls_unequal
myisam_use_mmap = OFF
net_buffer_length = 16384
net_read_timeout = 30
net_retry_count = 10
net_write_timeout = 60
new = OFF
old = OFF
old_alter_table = OFF
old_passwords = OFF
open_files_limit = 1024
optimizer_fix = ON
optimizer_prune_level = 1
optimizer_search_depth = 62
optimizer_switch = index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on
performance_schema = OFF
performance_schema_events_waits_history_long_size = 10000
performance_schema_events_waits_history_size = 10
performance_schema_max_cond_classes = 80
performance_schema_max_cond_instances = 1000
performance_schema_max_file_classes = 50
performance_schema_max_file_handles = 32768
performance_schema_max_file_instances = 10000
performance_schema_max_mutex_classes = 200
performance_schema_max_mutex_instances = 1000000
performance_schema_max_rwlock_classes = 30
performance_schema_max_rwlock_instances = 1000000
performance_schema_max_table_handles = 100000
performance_schema_max_table_instances = 50000
performance_schema_max_thread_classes = 50
performance_schema_max_thread_instances = 1000
pid_file = /var/lib/mysql/rhino0.forumhouse.ru.pid
plugin_dir = /usr/lib64/mysql/plugin/
port = 3306
preload_buffer_size = 32768
profiling = OFF
profiling_history_size = 15
protocol_version = 10
proxy_user = 
pseudo_slave_mode = OFF
pseudo_thread_id = 20749
query_alloc_block_size = 8192
query_cache_limit = 1048576
query_cache_min_res_unit = 4096
query_cache_size = 0
query_cache_strip_comments = OFF
query_cache_type = ON
query_cache_wlock_invalidate = OFF
query_prealloc_size = 8192
query_response_time_range_base = 10
query_response_time_stats = OFF
rand_seed1 = 0
rand_seed2 = 0
range_alloc_block_size = 4096
read_buffer_size = 131072
read_only = OFF
read_rnd_buffer_size = 262144
relay_log = 
relay_log_index = 
relay_log_info_file = relay-log.info
relay_log_purge = ON
relay_log_recovery = OFF
relay_log_space_limit = 0
report_host = 
report_password = 
report_port = 3306
report_user = 
rpl_recovery_rank = 0
secure_auth = OFF
secure_file_priv = 
server_id = 101
skip_external_locking = ON
skip_name_resolve = OFF
skip_networking = OFF
skip_show_database = OFF
slave_compressed_protocol = OFF
slave_exec_mode = STRICT
slave_load_tmpdir = /tmp
slave_max_allowed_packet = 1073741824
slave_net_timeout = 3600
slave_skip_errors = OFF
slave_transaction_retries = 10
slave_type_conversions = 
slow_launch_time = 2
slow_query_log = OFF
slow_query_log_always_write_time = 10.000000
slow_query_log_file = /var/lib/mysql/rhino0-slow.log
slow_query_log_timestamp_always = OFF
slow_query_log_timestamp_precision = second
slow_query_log_use_global_control = 
socket = /var/lib/mysql/mysql.sock
sort_buffer_size = 2097152
sql_auto_is_null = OFF
sql_big_selects = ON
sql_big_tables = OFF
sql_buffer_result = OFF
sql_log_bin = ON
sql_log_off = OFF
sql_low_priority_updates = OFF
sql_max_join_size = 18446744073709551615
sql_mode = 
sql_notes = ON
sql_quote_show_create = ON
sql_safe_updates = OFF
sql_select_limit = 18446744073709551615
sql_slave_skip_counter = 0
sql_warnings = OFF
ssl_ca = 
ssl_capath = 
ssl_cert = 
ssl_cipher = 
ssl_key = 
storage_engine = InnoDB
stored_program_cache = 256
sync_binlog = 1
sync_frm = ON
sync_master_info = 0
sync_relay_log = 0
sync_relay_log_info = 0
system_time_zone = MSK
table_definition_cache = 400
table_open_cache = 400
thread_cache_size = 0
thread_concurrency = 10
thread_handling = one-thread-per-connection
thread_pool_high_prio_mode = transactions
thread_pool_high_prio_tickets = 4294967295
thread_pool_idle_timeout = 60
thread_pool_max_threads = 100000
thread_pool_oversubscribe = 3
thread_pool_size = 24
thread_pool_stall_limit = 500
thread_stack = 262144
thread_statistics = OFF
time_format = %H:%i:%s
time_zone = SYSTEM
timed_mutexes = OFF
timestamp = 1406284321
tmp_table_size = 16777216
tmpdir = /tmp
transaction_alloc_block_size = 8192
transaction_prealloc_size = 4096
tx_isolation = REPEATABLE-READ
unique_checks = ON
updatable_views_with_limit = YES
userstat = OFF
version = 5.5.37-35.0-55-log
version_comment = Percona XtraDB Cluster (GPL), Release rel35.0, Revision 756, WSREP version 25.10, wsrep_25.10.r3985
version_compile_machine = x86_64
version_compile_os = Linux
wait_timeout = 28800
warning_count = 0
wsrep_OSU_method = TOI
wsrep_auto_increment_control = ON
wsrep_causal_reads = OFF
wsrep_certify_nonPK = ON
wsrep_cluster_address = gcomm://192.168.100.20,192.168.100.66
wsrep_cluster_name = fh_cluster
wsrep_convert_LOCK_to_trx = OFF
wsrep_data_home_dir = /var/lib/mysql/
wsrep_dbug_option = 
wsrep_debug = OFF
wsrep_desync = OFF
wsrep_drupal_282555_workaround = OFF
wsrep_forced_binlog_format = NONE
wsrep_load_data_splitting = ON
wsrep_log_conflicts = OFF
wsrep_max_ws_rows = 131072
wsrep_max_ws_size = 1073741824
wsrep_mysql_replication_bundle = 0
wsrep_node_address = 192.168.100.20
wsrep_node_incoming_address = AUTO
wsrep_node_name = rhino0.forumhouse.ru
wsrep_notify_cmd = 
wsrep_on = ON
wsrep_provider = /usr/lib64/libgalera_smm.so
wsrep_provider_options = base_host = 192.168.100.20; base_port = 4567; cert.log_conflicts = no; debug = no; evs.causal_keepalive_period = PT1S; evs.debug_log_mask = 0x1; evs.inactive_check_period = PT0.5S; evs.inactive_timeout = PT15S; evs.info_log_mask = 0; evs.install_timeout = PT15S; evs.join_retrans_period = PT1S; evs.keepalive_period = PT1S; evs.max_install_timeouts = 1; evs.send_window = 4; evs.stats_report_period = PT1M; evs.suspect_timeout = PT5S; evs.use_aggregate = true; evs.user_send_window = 2; evs.version = 0; evs.view_forget_timeout = P1D; gcache.dir = /var/lib/mysql/; gcache.keep_pages_size = 0; gcache.mem_size = 0; gcache.name = /var/lib/mysql//galera.cache; gcache.page_size = 128M; gcache.size = 128M; gcs.fc_debug = 0; gcs.fc_factor = 1.0; gcs.fc_limit = 16; gcs.fc_master_slave = no; gcs.max_packet_size = 64500; gcs.max_throttle = 0.25; gcs.recv_q_hard_limit = 9223372036854775807; gcs.recv_q_soft_limit = 0.25; gcs.sync_donor = no; gmcast.listen_addr = tcp://0.0.0.0:4567; gmcast.mcast_addr = ; gmcast.mcast_ttl = 1; gmcast.peer_timeout = PT3S; gmcast.time_wait = PT5S; gmcast.version = 0; ist.recv_addr = 192.168.100.20; pc.announce_timeout = PT3S; pc.checksum = false; pc.ignore_quorum = false; pc.ignore_sb = false; pc.linger = PT20S; pc.npvo = false; pc.version = 0; pc.wait_prim = true; pc.wait_prim_timeout = P30S; pc.weight = 1; protonet.backend = asio; protonet.version = 0; repl.causal_read_timeout = PT30S; repl.commit_order = 3; 
wsrep_recover = OFF
wsrep_reject_queries = NONE
wsrep_replicate_myisam = OFF
wsrep_restart_slave = OFF
wsrep_retry_autocommit = 1
wsrep_slave_threads = 1
wsrep_sst_auth = ********
wsrep_sst_donor = 
wsrep_sst_donor_rejects_queries = OFF
wsrep_sst_method = xtrabackup-v2
wsrep_sst_receive_address = AUTO
wsrep_start_position = 025e2495-11ae-11e4-9bd8-b7ff319b2780:9